It is known that, in automotive applications, the rolling bearings, in particular those present in wheel hubs, and more in particular those forming the hub bearing unit of the aforesaid type, are continuously exposed, in use, to the contact with high quantities of contaminants: therefore, in such applications, the sealing assemblies used to protect the bearings (incorporated in the bearings themselves or, more frequently, belonging to the hub-bearing unit) in addition to the purpose of withholding the lubricant oil or grease within the bearing, above all have the purpose of preventing external contaminants from entering inside the wheel hub and/or the bearing.
Unfortunately, contaminants such as dust and mud, also if blocked by the sealing assembly, tend to blend with the grease lubricating the sealing lips and wear the latter off until they lose their entire sealing capacity. To overcome such drawback, the sealing assemblies known for the described applications present a main radial sealing lip and, more outwards, a dust lip for preserving the main lip from the contact with contaminants.
However, to avoid a rapid wear thereof, the anti-dust lips are usually designed so as to fit with the sealing surface on which the main lip cooperates by interference, with very low interference or even with minor clearance. In this way, however, the lubricant grease possibly placed between the two lips is easily lost outwards and the external contaminants, also if in minimum amount, may come into contact with the main sealing lip and cause consequent wear of the same.
A solution of the problem consists in shaping the anti-dust lip so as to “pump” the contaminants outwards. However, such solution is no longer satisfying in view of the longer life required by the members.